Mesoscale Cyclogenesis over the Southwestern Ross Sea Linked to Strong Katabatic Winds

Abstract

Two years of automatic weather station (AWS) observations and satellite images have been used to study mesoscale cyclogenesis along the Transantarctic Mountains. Twice-daily regional sea-level pressure analyses revealed the frequent formation of mesoscale cyclones adjacent to two regions where the discharge of cold boundary-layer air from east Antarctica is concentrated: near Terra Nova Bay/Franklin Island and Byrd Glacier. Between one and two new vortices on average formed each week in the former location with weak frequency maxima in December?March and August?September. There was a large difference between the cyclogenetic activity in the two years. The AWS array expanded in 1985 and resolved another cyclogenetic area near Byrd Glacier. This feature was half as active as the Franklin Island area and exhibited many of the same characteristics. About half of the Byrd Glacier cyclones developed simultaneously with vortices near Franklin Island. These developments are the result of a dry baroclinic process with marked baroclinicity and weak cyclonic vorticity appearing to be boundary-layer prerequisites. There is little consistent upper-air support associated with the cyclogeneses, but such factors often play a key role in subsequent storm evolution. The evidence suggests that synoptic forcing plays a significant genetic role via troughs attached to, but ahead of, maritime cyclones centered to the northwest of the Ross Sea.